Dutch airline KLM and German airline Lufthansa have carried out test flights to see if it is safe for planes to fly.

Britain has extended a ban on most flights in its airspace until at least 1800 GMT Sunday, air authorities have said.

KLM said its plane, a Boeing 737, had reached its maximum operating altitude of about 13km in the skies over the Netherlands, and there had been no problems during the flight.

The aircraft and its engines were being inspected for possible damage. After the results of that technical inspection the airline hopes to get permission from the aviation authorities to start up operations again.

Germany's Lufthansa said it flew several planes to Frankfurt from Munich.

A spokesman said: "All airplanes have been inspected on arrival in Frankfurt but there was no damage to the cockpit windows or fuselage and no impact on the engines."

Earlier, a spokesman for the international airline industry said: "We don't see the light at the end of the tunnel yet."

Icelandic geologist Magnus Tumi Gudmundsson told the Associated Press news agency: "It's the magma mixing with the water that creates the explosivity. Unfortunately, there doesn't seem to be an end in sight."

Graeme Leitch, a meteorologist at Britain's National Weather Service, said light winds and high pressure over Europe meant the cloud was unlikely to be dispersed soon.

"We don't expect a great deal of change over the next few days," he told AP.

The International Air Transport Association (IATA) predicted little or no improvement on Sunday.

"Right now through most of Europe we do not see many flights moving at all," spokesman Steve Lott told AFP news agency.

Airlines are losing some £130m ($200m) a day in an unprecedented shutdown of commercial air travel, the IATA says.

Eurocontrol, which co-ordinates air traffic control in 38 nations, said it expected 17,000 flights to be cancelled across Europe on Saturday, from a total of 22,000 on a normal day.

Long way home

Since Thursday, countries across northern and central Europe have either closed airspace or shut key airports as the ash - a mixture of glass, sand and rock particles - can seriously damage aircraft engines.

In the UK commercial flights have now been banned until at least 0700 local time (0600 GMT) on Sunday.

In northern France and northern Italy, airports are to remain shut until at least Monday.

Unable to catch flights, commuters across northern Europe have sought other means of transport, packing out trains, buses and ferries.

The Eurostar cross-channel rail service said it had never seen so many passengers on one day and the trains were fully booked until Monday.

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